Ultrasonic probe

ABSTRACT

An ultrasonic probe according to one embodiment, includes a first wiring plate, a second wiring plate and a vibrator. The vibrator is provided between the first wiring plate and the second wiring plate. The vibrator includes a backing material provided on the first wiring plate, a piezoelectric body provided on the backing material, a first acoustic matching layer provided on the piezoelectric body, a second acoustic matching layer provided on the first acoustic matching layer, a first bonding layer having conductive properties and bonding the backing material and the piezoelectric body, a second bonding layer bonding the piezoelectric body and the first acoustic matching layer, and a third bonding layer having insulating properties and bonding the first acoustic matching layer and the second acoustic matching layer.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is based upon and claims the benefit of priority fromJapanese Patent Application No. 2014-057913, filed on Mar. 20, 2014; theentire contents of which are incorporated herein by reference.

FIELD

Embodiments described herein relate to an ultrasonic probe.

BACKGROUND

An ultrasonic probe is developed and is used in the medical field or thelike. The ultrasonic probe transmits ultrasonic waves to a target,receives ultrasonic waves reflected back from the target, and therebyforms an image of a shape of the target In such an ultrasonic probe, aplurality of vibrators are arranged between two wiring plates in onedimension or in two dimensions. In each of the vibrators, a backingmaterial, a piezoelectric body, and an acoustic matching layer arestacked in this order. The backing material and the piezoelectric body,and the piezoelectric body and the acoustic matching layer are bonded bybonding layers, respectively.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a side view illustrating an ultrasonic probe according to afirst embodiment;

FIG. 2 is a cross-sectional view illustrating a vibrator of theultrasonic probe shown in FIG. 1;

FIG. 3 is a cross-sectional view illustrating a conductive bonding layerof the vibrator shown in FIG. 2;

FIGS. 4A and 4B are cross-sectional views illustrating a method ofmanufacturing the ultrasonic probe according to the first embodiment;

FIG. 5 is a cross-sectional view illustrating a vibrator of anultrasonic probe according to a second embodiment; and

FIG. 6 is a cross-sectional view illustrating a vibrator of anultrasonic probe according to a third embodiment.

DETAILED DESCRIPTION

An ultrasonic probe according to one embodiment, includes a first wiringplate, a second wiring plate and a vibrator. The vibrator is providedbetween the first wiring plate and the second wiring plate. The vibratorincludes a backing material provided on the first wiring plate, apiezoelectric body provided on the backing material, a first acousticmatching layer provided on the piezoelectric body, a second acousticmatching layer provided on the first acoustic matching layer, a firstbonding layer having conductive properties and bonding the backingmaterial and the piezoelectric body, a second bonding layer bonding thepiezoelectric body and the first acoustic matching layer, and a thirdbonding layer having insulating properties and bonding the firstacoustic matching layer and the second acoustic matching layer.

First Embodiment

Hereinafter, an embodiment of the invention will be described withreference to the drawings.

First, a first embodiment is described.

FIG. 1 is a side view illustrating an ultrasonic probe according to theembodiment.

FIG. 2 is a cross-sectional view illustrating a vibrator of theultrasonic probe shown in FIG. 1.

FIG. 3 is a cross-sectional view illustrating a conductive bonding layerof the vibrator shown in FIG. 2.

As illustrated in FIG. 1, in an ultrasonic probe 1 according to theembodiment, two flexible printed wiring plates 11 and 12 are provided inparallel to and spaced from each other. In the flexible printed wiringplates (hereinafter, simply referred to as “wiring plate”) 11 and 12,wiring (not illustrated) is printed on a surface of a substrate that isformed of a resin material. For example, hundreds of vibrators 20 areprovided so as to be arranged in a row between the wiring plate 11 andthe wiring plate 12. Each vibrator 20 is strip-shaped.

As illustrated in FIG. 2, in each vibrator 20, a backing material 21, apiezoelectric body 22, an acoustic matching layer 23, and an acousticmatching layer 24 (hereinafter, collectively referred to as “member”)are stacked in this order from the wiring plate 11 toward the wiringplate 12. The backing material 21 absorbs sound from the piezoelectricbody 22 toward the wiring plate 11 and is a member for suppressingresidual vibration. For example, the backing material 21 is formed ofcemented carbide and has a thickness of appropriately hundreds of μm(micron). When a voltage is applied, the piezoelectric body 22 vibrates,when vibration is applied, the piezoelectric body 22 transmits thevoltage, and the piezoelectric body 22 functions as a transmittingelement and as a receiving element of the ultrasonic waves. Thepiezoelectric body 22 is made of, for example, lead zirconium titanate(PZT) and has a thickness of appropriately 200 μm to 300 μm.

The acoustic matching layers 23 and 24 adjust acoustic impedance and aremembers for efficiently inputting the ultrasonic waves to the target.The acoustic matching layer 23 is made of, for example, glass and has athickness of appropriately 200 μm to 300 μm. In addition, the acousticmatching layer 24 is made of, for example, carbon and has a thickness ofappropriately 100 μm. Rigidity is increased in the order of the backingmaterial 21, the piezoelectric body 22, the acoustic matching layer 23,the acoustic matching layer 24, and the wiring plates 11 and 12. Thatis, the backing material 21 has the highest rigidity, next thepiezoelectric body 22 has high rigidity. In addition, gold plating isperformed on surfaces of the members, but gold plating is not performedon surfaces facing each other in the backing material 21 and thepiezoelectric body 22.

In addition, an insulative bonding layer 31 is provided between thewiring plate 11 and the backing material 21, and the backing material 21is bonded to the wiring plate 11. A conductive bonding layer 32 isprovided between the backing material 21 and the piezoelectric body 22and the piezoelectric body 22 is bonded to the backing material 21. Aninsulative bonding layer 33 is provided between the piezoelectric body22 and the acoustic matching layer 23, and the acoustic matching layer23 is bonded to the piezoelectric body 22. An insulative bonding layer34 is provided between the acoustic matching layer 23 and the acousticmatching layer 24, and the acoustic matching layer 24 is bonded to theacoustic matching layer 23. An insulative bonding layer 35 is providedbetween the acoustic matching layer 24 and the wiring plate 12 and thewiring plate 12 is bonded to the acoustic matching layer 24.

As above, among the bonding layer by which the vibrator 20 is bonded tothe wiring plates 11 and 12, and bonding layers by which members of thevibrator 20 are bonded to each other, only the conductive bonding layer32 has conductive properties, and other bonding layers have insulatingproperties. The thickness of the conductive bonding layer 32 isappropriately 2 μm to 10 μm, and the thickness of the insulative bondinglayers 31, and 33 to 35 is 2 μm to 3 μm. When the thickness of theinsulative bonding layer is equal to or less than 2 μm to 3 μm, theunevenness of surfaces of the members is not covered completely. Sincefine convex portions on the surfaces come into contact with each other,the members are connected electrically to each other. When theinsulative bonding layer becomes excessively thick, the convex portionson the surfaces of the members do not come into contact with each otherand then the members are nonconductive to each other. As a result, avoltage is not applied to the piezoelectric body 22 and the vibrator 20is defective.

As illustrated in FIG. 3, in the conductive bonding layer 32, aplurality of fillers 32 b are dispersed in the base material 32 a whichis made of a resin material. The base material 32 a is formed of, forexample, a thermosetting resin and, for example, is formed of an epoxyresin. The filler 32 b is formed of conductive material, and of, forexample silver or carbon. There is no particular limitation to the shapeof the filler 32 b and, the filler 32 b has, for example, a grain shape,a needle shape, or a thin plate shape. The maximum diameter of thefiller 32 b is less than the thickness of the conductive bonding layer32. The filler is not provided in the insulative bonding layers 31, and33 to 35, and the insulative bonding layers are formed of thermosettingresin material, for example, an epoxy resin.

Next, a method of manufacturing the ultrasonic probe according to theembodiment is described.

FIGS. 4A and 4B are cross-sectional views illustrating the method ofmanufacturing the ultrasonic probe according to the embodiment.

In FIGS. 4A and 4B, bending of the members is illustrated to beconspicuous.

First, as illustrated in FIG. 4A, the backing material 21, thepiezoelectric body 22, the acoustic matching layer 23, and the acousticmatching layer 24 are stacked in this order on the flexible printedwiring plate 11 through the bonding layers 31 to 34 (refer to FIG. 2)and form a stacked body 29. At this time, the shapes of the members are,for example, a rectangular plate shape of which the length is 60 mm to70 mm (millimeter) and the width is 15 mm. At this stage, the bendingoccurs in the members, but the extent of the bending is different fromeach other depending on the members. For example, the bending of thebacking material 21 is appropriately 10 μm, the bending of thepiezoelectric body 22 is appropriately 40 μm, the bending of theacoustic matching layer 23 is appropriately 20 μm, and the bending ofthe acoustic matching layer 24 is appropriately 120 μm. Therefore, gapsS1 to S4 are formed between the members due to the bending difference.The gaps S1 to S4 are filled with the insulative bonding layer 31, theconductive bonding layer 32, the insulative bonding layer 33, and theinsulative bonding layer 34, respectively.

Next, as illustrated in FIG. 4B, a compressive force is applied to thestacked body 29 in a direction in which the wiring plate 11 and theacoustic matching layer 24 come closer to each other and the bending ofthe members is corrected. Thus, the gaps S1 to S4 are decreased andbecome uniform. However, at this time, among the members, it isdifficult to sufficiently correct the gap S2 formed between the backingmaterial 21 which has the highest rigidity and the piezoelectric body 22which has the second-highest rigidity. The gap S2 remains non-uniform.Next, a heating treatment is performed, and the insulative bonding layer31, the conductive bonding layer 32, the insulative bonding layer 33,and the insulative bonding layer 34 are cured thermally. Thus, themembers are bonded to each other.

Next, as illustrated in FIG. 1, the stacked body 29 is subjected todicing and divided into a plurality of vibrators 20. Next, the wiringplate 12 is disposed on the vibrator 20 through the insulative bondinglayer 35. Next, the heating treatment is performed, and the insulativebonding layer 35 is cured thermally. As described above, the ultrasonicprobe 1 is manufactured.

Next, effects of the embodiment are described.

As described above, in a process shown in FIG. 4B, even when acompressive force is applied to the stacked body 29, it is difficult tosufficiently correct the gap S2 formed between the backing material 21that has the highest rigidity and the piezoelectric body 22 that has thesecond-highest rigidity. Therefore, in the manufactured ultrasonic probe1, the conductive bonding layer 32 is thicker than other bonding layersin some vibrators 20. However, in the embodiment, since the conductivebonding layer 32 has conductive properties, it is possible to secure theconductivity between the backing material 21 and the piezoelectric body22 even when the conductive bonding layer 32 becomes thick. Therefore,the ultrasonic probe 1 has a high electrical reliability. In addition,in the embodiment, it is possible not to perform the gold plating on thesurfaces facing each other in the backing material 21 and thepiezoelectric body 22. Thus, it is possible to reduce a cost ofmanufacturing the ultrasonic probe 1.

If an insulative bonding layer is provided instead of the conductivebonding layer 32, the gap S2 is not sufficiently corrected, and when theinsulative bonding layer is thick in several vibrators 20, the convexportion on the surface of the backing material 21 and the convex portionon the surface of the piezoelectric body 22 do not come into contactwith each other, and thus the backing material 21 and the piezoelectricbody 22 become non-conductive to each other. In addition, in the processshown in FIG. 4B, it is considered that a strong force is applied to thestacked body 29 and thereby the gap S2 is caused to be sufficientlythin; however, in this case, the bonding layers which have small gapsoriginally become too thin, and then the bonding force is degraded. As aresult, when dicing is performed on the stacked body 29, there is apossibility that a part of vibrators 20 are broken.

In addition, in the embodiment, between the wiring plate 11 and thebacking material 21, between the piezoelectric body 22 and the acousticmatching layer 23, between the acoustic matching layer 23 and theacoustic matching layer 24, and between the acoustic matching layer 24and the wiring plate 12, the insulative bonding layers 31, 33, 34, and35 are disposed, respectively. When comparing the insulative bondinglayer and the conductive bonding layer, the insulative bonding layer hasa higher bonding force by portions where the fillers are not dispersed.Therefore, these members are bonded strongly to each other and theultrasonic probe 1 according to the embodiment has a high mechanicalreliability.

Since the fillers which do not contribute to bonding are contained inthe conductive bonding layer, the bonding strength is lower compared tothe insulative bonding layer. Therefore, if all the bonding layers arethe conductive bonding layer, the mechanical strength of the entireultrasonic probe is lowered and thus reliability is lowered.

Second Embodiment

Next, a second embodiment is described.

FIG. 5 is a cross-sectional view illustrating a vibrator of anultrasonic probe according to the embodiment.

As illustrated in FIG. 5, an ultrasonic probe 2 according to theembodiment includes a conductive bonding layer 43 instead of theinsulative bonding layer 33, which is a difference compared to theultrasonic probe 1 (refer to FIG. 2) according to the first embodimentdescribed above.

In the embodiment, among the members, the piezoelectric body 22 that hasthe second-highest rigidity and the acoustic matching layer 23 that hasthe third-highest rigidity are bonded by the conductive bonding layer43. Since the gap S3 between the piezoelectric body 22 and the acousticmatching layer 23 is reduced following the gap S2, the gap S3 is filledwith the conductive bonding layer 43, and thereby it is possible toreliably prevent failure of conduction. In the embodiment,configurations other than that described above, a method ofmanufacturing and the effects are the same as in the first embodiment.

Third Embodiment

Next, a third embodiment is described. FIG. 6 is a cross-sectional viewillustrating a vibrator of an ultrasonic probe according to theembodiment.

As illustrated in FIG. 6, an ultrasonic probe 3 according to theembodiment includes a conductive bonding layer 42 instead of theconductive bonding layer 32, which is a difference compared to theultrasonic probe 1 (refer to FIG. 2) according to the first embodimentdescribed above. The conductive bonding layer 42 is not formed of theepoxy resin in which fillers are dispersed, but is configured to have ananisotropic conductive film (ACF). In the embodiment, configurationsother than that described above, a method of manufacturing and theeffects are the same as in the first embodiment.

According to the embodiment described above, it is possible to realizethe ultrasonic probe with high reliability.

While certain embodiments have been described, these embodiments havebeen presented by way of example only, and are not intended to limit thescope of the inventions. Indeed, the novel embodiments described hereinmay be embodied in a variety of other forms; furthermore, variousomissions, substitutions and changes in the form of the embodimentsdescribed herein may be made without departing from the spirit of theinventions. The accompanying claims and their equivalents are intendedto cover such forms or modifications as would fall within the scope andspirit of the invention. Additionally, the embodiments described abovecan be combined mutually.

What is claimed is:
 1. An ultrasonic probe comprising: a first wiringplate; a second wiring plate; and a vibrator provided between the firstwiring plate and the second wiring plate, the vibrator including: abacking material provided on the first wiring plate; a piezoelectricbody provided on the backing material; a first acoustic matching layerprovided on the piezoelectric body; a second acoustic matching layerprovided on the first acoustic matching layer; a first bonding layerhaving conductive properties and bonding the backing material and thepiezoelectric body; a second bonding layer bonding the piezoelectricbody and the first acoustic matching layer; and a third bonding layerhaving insulating properties and bonding the first acoustic matchinglayer and the second acoustic matching layer.
 2. The probe according toclaim 1, wherein the second bonding layer has insulating properties. 3.The probe according to claim 1, wherein the second bonding layer hasconductive properties.
 4. The probe according to claim 1, wherein thebacking material has higher rigidity than the piezoelectric body, thepiezoelectric body has higher rigidity than the first acoustic matchinglayer, and the first acoustic matching layer has higher rigidity thanthe second acoustic matching layer.
 5. The probe according to claim 1,wherein the first bonding layer includes: a base material which isformed of a resin material; and a conductive filler dispersed in thebase material.
 6. The probe according to claim 5, wherein the basematerial is a thermosetting resin material.
 7. The probe according toclaim 6, wherein the thermosetting resin material is an epoxy resin. 8.The probe according to claim 5, wherein the filler is formed of silver.9. The probe according to claim 5, wherein the filler is formed ofcarbon.
 10. The probe according to claim 5, wherein a maximum diameterof the filler is less than a thickness of the first bonding layer. 11.The probe according to claim 1, wherein the first bonding layer is ananisotropic conductive film.
 12. The probe according to claim 1, whereinthe first bonding layer has a greater thickness than the third bondinglayer.
 13. The probe according to claim 1, wherein the first bondinglayer has a thickness of 2 μm to 10 μm.
 14. The probe according to claim1, wherein the third bonding layer has a thickness of 2 μm to 3 μm. 15.An ultrasonic probe comprising: a first wiring plate; a second wiringplate; and a vibrator provided between the first wiring plate and thesecond wiring plate, the vibrator including: a plurality of membersstacked from the first wiring plate toward the second wiring plate; anda plurality of bonding layers bonding the adjacent members, and a firstbonding layer of the plurality of bonding layers bonding a member thathas the highest rigidity and a member that has the second-highestrigidity among the plurality of members, the first bonding layer havingconductive properties, a second bonding layer of the plurality ofbonding layers bonding a member that has lowest rigidity and a memberthat has the second-lowest rigidity among the plurality of members, thesecond bonding layer having insulating properties.
 16. The probeaccording to claim 15, wherein the member that has the highest rigidityis a backing material, the member that has the second-highest rigidityis a piezoelectric body, and the member that has the lowest rigidity isan acoustic matching layer.